聊聊Elasticsearch RestClient的NodeSelector

旧城等待， 2022-01-17 09:55 218阅读 0赞

[为什么80%的码农都做不了架构师？>>> ][80_]  ![hot3.png][]

## 序 ##

本文主要研究一下Elasticsearch RestClient的NodeSelector

## NodeSelector ##

elasticsearch-7.0.1/client/rest/src/main/java/org/elasticsearch/client/NodeSelector.java

public interface NodeSelector {
        /**
         * Select the {@link Node}s to which to send requests. This is called with
         * a mutable {@link Iterable} of {@linkplain Node}s in the order that the
         * rest client would prefer to use them and implementers should remove
         * nodes from the that should not receive the request. Implementers may
         * iterate the nodes as many times as they need.
         * <p>
         * This may be called twice per request: first for "living" nodes that
         * have not been blacklisted by previous errors. If the selector removes
         * all nodes from the list or if there aren't any living nodes then the
         * {@link RestClient} will call this method with a list of "dead" nodes.
         * <p>
         * Implementers should not rely on the ordering of the nodes.
         */
        void select(Iterable<Node> nodes);
        /*
         * We were fairly careful with our choice of Iterable here. The caller has
         * a List but reordering the list is likely to break round robin. Luckily
         * Iterable doesn't allow any reordering.
         */
    
        /**
         * Selector that matches any node.
         */
        NodeSelector ANY = new NodeSelector() {
            @Override
            public void select(Iterable<Node> nodes) {
                // Intentionally does nothing
            }
    
            @Override
            public String toString() {
                return "ANY";
            }
        };
    
        /**
         * Selector that matches any node that has metadata and doesn't
         * have the {@code master} role OR it has the data {@code data}
         * role.
         */
        NodeSelector SKIP_DEDICATED_MASTERS = new NodeSelector() {
            @Override
            public void select(Iterable<Node> nodes) {
                for (Iterator<Node> itr = nodes.iterator(); itr.hasNext();) {
                    Node node = itr.next();
                    if (node.getRoles() == null) continue;
                    if (node.getRoles().isMasterEligible()
                            && false == node.getRoles().isData()
                            && false == node.getRoles().isIngest()) {
                        itr.remove();
                    }
                }
            }
    
            @Override
            public String toString() {
                return "SKIP_DEDICATED_MASTERS";
            }
        };
    }

## HasAttributeNodeSelector ##

elasticsearch-7.0.1/client/rest/src/main/java/org/elasticsearch/client/HasAttributeNodeSelector.java

public final class HasAttributeNodeSelector implements NodeSelector {
        private final String key;
        private final String value;
    
        public HasAttributeNodeSelector(String key, String value) {
            this.key = key;
            this.value = value;
        }
    
        @Override
        public void select(Iterable<Node> nodes) {
            Iterator<Node> itr = nodes.iterator();
            while (itr.hasNext()) {
                Map<String, List<String>> allAttributes = itr.next().getAttributes();
                if (allAttributes == null) continue;
                List<String> values = allAttributes.get(key);
                if (values == null || false == values.contains(value)) {
                    itr.remove();
                }
            }
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            HasAttributeNodeSelector that = (HasAttributeNodeSelector) o;
            return Objects.equals(key, that.key) &&
                    Objects.equals(value, that.value);
        }
    
        @Override
        public int hashCode() {
            return Objects.hash(key, value);
        }
    
        @Override
        public String toString() {
            return key + "=" + value;
        }
    }

*  HasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会删除node的attributes没有该key或者该key对应的value为null的node

## PreferHasAttributeNodeSelector ##

elasticsearch-7.0.1/client/rest/src/main/java/org/elasticsearch/client/PreferHasAttributeNodeSelector.java

public final class PreferHasAttributeNodeSelector implements NodeSelector {
        private final String key;
        private final String value;
    
        public PreferHasAttributeNodeSelector(String key, String value) {
            this.key = key;
            this.value = value;
        }
    
        @Override
        public void select(Iterable<Node> nodes) {
            boolean foundAtLeastOne = false;
    
            for (Node node : nodes) {
                Map<String, List<String>> attributes = node.getAttributes();
    
                if (attributes == null) {
                    continue;
                }
    
                List<String> values = attributes.get(key);
    
                if (values == null) {
                    continue;
                }
    
                if (values.contains(value)) {
                    foundAtLeastOne = true;
                    break;
                }
            }
    
            if (foundAtLeastOne) {
                Iterator<Node> nodeIterator = nodes.iterator();
                while (nodeIterator.hasNext()) {
                    Map<String, List<String>> attributes = nodeIterator.next().getAttributes();
    
                    if (attributes == null) {
                        continue;
                    }
    
                    List<String> values = attributes.get(key);
    
                    if (values == null || !values.contains(value)) {
                        nodeIterator.remove();
                    }
                }
            }
        }
    
        @Override
        public boolean equals(Object o) {
            if (this == o) {
                return true;
            }
            if (o == null || getClass() != o.getClass()) {
                return false;
            }
            PreferHasAttributeNodeSelector that = (PreferHasAttributeNodeSelector) o;
            return Objects.equals(key, that.key) &&
                Objects.equals(value, that.value);
        }
    
        @Override
        public int hashCode() {
            return Objects.hash(key, value);
        }
    
        @Override
        public String toString() {
            return key + "=" + value;
        }
    }

*  PreferHasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会先遍历nodes设置foundAtLeastOne，如果foundAtLeastOne为true才会删除node的attributes没有该key或者该key对应的value为null的node

## 小结 ##

*  NodeSelector接口定义了select方法，它接收mutable的Iterable，然后具体实现会选择性删除node；它定义了ANY、SKIP\_DEDICATED\_MASTERS两个匿名实现类，其中ANY的select方法不做任何操作；SKIP\_DEDICATED\_MASTERS的select方法会删除date为false、ingest为false的master node
 *  HasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会删除node的attributes没有该key或者该key对应的value为null的node
 *  PreferHasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会先遍历nodes设置foundAtLeastOne，如果foundAtLeastOne为true才会删除node的attributes没有该key或者该key对应的value为null的node

## doc ##

*  [Node selector][]

转载于:https://my.oschina.net/go4it/blog/3050101

[80_]: https://my.oschina.net/u/2663968/blog/3051541
[hot3.png]: /images/20220117/97969a6bb4c140de8745b4e5665957bd.png
[Node selector]: https://www.elastic.co/guide/en/elasticsearch/client/java-rest/master/_node_selector.html